With the present relatively high cost of telephone calls, it is important that the unauthorised use of a telephone is prevented. A particular problem arises where babysitters, children or the like are left for long periods of time in a house on their own. Without the knowledge of the house owner, they can make unlimited numbers of telephone calls to unlimited destinations. It is impossible to positively determine whether a particular individual or not made the calls. Furthermore, there are many cases where it is necessary to prevent access to at least some, if not all, of the keys of a keyboard of, for example, a computer, a cash register, a typewriter or the like. There is therefore a need for a security device which can readily easily be fitted to a telephone to prevent access to at least some of the digit keys of a digital telephone which overcomes the problems and disadvantages of known devices. Indeed, there is also a need for such a security device which may be fitted to any keyboard, for example, a computer keyboard or the like, similarly to prevent access to at least some of the keys.
Attempts have been made to provide security devices for telephones. However, these devices have not been entirely successful. In general, such devices comprise a base framework which is secured to the housing of the telephone and a cover which is usually pivotally or releasably connected to the framework. The cover extends over the keypad of the telephone to prevent access to the digit keys. A padlock or barrel lock is usually provided for locking the cover to the base framework. Two such devices are disclosed in U.S. Pat. Nos. 3,866,000 and 3,965,310. These devices suffer from a number of disadvantages. In particular, because of the type of locking arrangements used, they, in general, tend to be cumbersome and also relatively expensive. A disadvantage of devices which require a padlock to secure the cover to the base framework is that because of the construction of these devices, the portion of the framework which engages the cover, or vice versa, can very easily break off and render the device thus useless. A further problem with padlock devices is that the padlock can be easily mislaid, or the keys of the padlock can similarly be easily mislaid.